In recent years, sales sites for conducting electronic commerce over the Internet are becoming popular. For example, a sales site (a shopping mall site) composed of a collection of many stores (virtual stores) are attracting many users since such sales site not only provides products of broad categories (genres) as a whole, but often provides price competition among the stores.
In such a sales site, respective products (products in each store) are managed and classified into hierarchical categories, and a list of products is displayed on a user terminal that has accessed the sales site. In addition, the sales site is also capable of displaying a list of products that is obtained based on a search condition (for example, a keyword) entered by a user in a predetermined order (for example, in order of popularity or sales price).
Patent Literature 1 discloses an example conventional technology for such sales site which is a server device to guarantee the credibility of a sales price that is displayed on a webpage.